1. Field of the Invention
The present invention relates to systems, devices and methods for acquiring, measuring, monitoring, processing and analyzing physiological signals. More particularly, the present invention relates to using physiological signals to determine a subject's response to various conditions, variables or constraints. Still more particularly, the present invention relates to monitoring the subject's external body motion and/or environmental factors and determining the amount of pain a subject is suffering as a result of the motion and factors. Still more particularly, the present invention relates to a system, device and methods of quantifying a subject's pain to provide an objective measurement of the subject's pain. The present invention further relates to establishing and improving pain management protocols and therapy or treatment for the subject's pain based on the quantified pain measurement.
2. Technology Review
Chronic pain affects as much as 30% of the population and is defined as pain persisting beyond a period of normal tissue healing, and/or experienced every day for 3 months or more. Chronic low back pain (CLBP) affects approximately one quarter of adults in any given year and is the most common cause of physical disability in the working population. While not a disease, people with CLBP report that most, if not all, aspects of their lives are significantly affected by their pain, and it can have a similar impact on health-related quality of life (QOL) as liver disease and cancer. Chronic pain has a significant economic impact, with an estimated health care cost of $300 billion per year. The pathophysiology of pain is not always well defined, which contributes to inconsistent patient outcomes, especially considering the reliance on patient-reported subjective outcomes. While the patient's perspective is an integral component, both treatment and research into chronic pain are greatly compromised by the fact that there is no objective diagnostic test that can complement the subjective assessment of chronic pain conditions.
Spinal cord stimulation (SCS) is the most common form of neuromodulation used in managing chronic back or leg pain, with more than 14,000 SCS implantations performed worldwide each year. SCS is a minimally invasive treatment in which electrodes are placed in the epidural space and masks pain by substituting it with paresthesia. A permanent implant is typically preceded by a trial evaluation during which the electrodes are placed percutaneously and connected to a small external stimulator. SCS has a success rate of about 50%, with sustained decreases pain intensity scores, functional improvement, and decreased medication usage. Recent evidence from off-label studies of deep brain stimulation, a more invasive form of neuromodulation, supports its use in treating forms of neuropathic pain and depression that are resistant to conventional treatments. An emerging form of neuromodulation which uses high frequency stimulation to block nerve conduction has shown promise for blocking pain transmission and is being commercialized for amputation pain. Despite these advances in the technological aspects of therapy, efficacy is universally judged by a reduction in subjective patient-reported severity, which is an important yet incomplete assessment of pain's impact on quality of life.
A number of validated tools, such as the visual analog scale and numerical rating scale and patient global impression scale, have been used to assess pain intensity. There are also a number of measures that assess the impact back pain has on function and QOL, including the pain self-efficacy scale and Oswestry disability index, but they have several limitations including: 1) they rely on self-reporting and recall, which are subjective and prone to bias, 2) they cannot be used in subjects with cognitive or communication impairments, and 3) they are not electronically time stamped and fail to capture the dynamic nature of pain and its impact on daily life.
Functional brain imaging (e.g., fMRI) has been proposed as an objective biomarker for pain intensity and perception. While imaging may eventually accurately capture pain perception, scans in the lab will not measure the effect of pain on QOL and independence, which are arguably the most important outcomes.
A number of sensors and sensing modalities are known to be useful in the measurement of pain, typically physiological signal sensors used to measure bioelectrical signals from a subject, for example EEG sensors. However, many other sensors and sensing modalities are not typically known to be useful in applications for measuring a subject's pain. For example, movement sensors such as accelerometers, gyroscopes, magnetometers, resistive bend sensors and the like, designed to measure a subject's external body motion, are not known in the art to be generally useful for measuring a subject's pain. Similarly, other sensors and sensing modalities such as audio and speech sensors, sleep sensors, video sensors, global positioning (GPS) sensors, skin conductance sensors, pulse oximeters, and even some physiological signal sensors are not generally known to be useful for pain measurement.
It is therefore an object of the present invention to: 1) effectively combine kinematic data from accelerometers and gyroscopes, and other sensor data related to physiological characteristic affected by chronic pain, with location, diary, and speech information obtained through data acquisition devices including, for example, smart phones, tablet computers, laptop computers, and the like, into a powerful research tool, and 2) provide objective measures in the clinical market to quantify and optimize therapeutic response to treatments. It is further an object of the present invention to provide accurate, objective monitoring of behavioral patterns of physical activity with sensors that may provide an accurate, objective appraisal of the impact of pain on the physical, social, and emotional functioning that complements standard patient-reported outcome measures. Given the challenges and opportunities outlined above, we aim to create an objective assessment method, system or device that will utilize motion sensors, other sensors related to physiological characteristics affected by chronic pain, GPS, and processing and interface components (such as a smart phone application, or “app”) to monitor physical activity, location, and self-reported information on pain level and QOL. Still further, it is an object of the present invention that the method, system or device can be used to help manage chronic pain patients, enabling them to capture objective data related to therapeutic response. In addition to chronic pain, it is an object of the present invention that the method, system or device will have implications for other monitoring disorders (e.g., depression) that affect behavioral patterns and rely on subjective patient self-assessment. It is yet a further object of the present invention that the method, system or device could be adapted in other programs as a telemedicine platform for delivering behavioral therapy, which has been shown to be a potential mechanism for expanding health care access for pain patients.